docs: 📝 update readme instructions

README.md

@@ -26,10 +26,18 @@ TODO
 
 TODO
 
-```sh
-deno task start # Local watch mode
+### Local watch mode
 
-deno task build && deno task serve # Production run
+```sh
+mkcert -install # If mkcert is not installed in your root ca
+mkcert -ecdsa localhost # Only once to issue localhost certificates
+deno task start
+```
+
+### Production run
+
+```sh
+deno task build && deno task serve
 ```
 
 ## 🤝 Contributing
@@ -43,6 +51,8 @@ Any kind of contribution is welcomed. Please read
 **Required dependencies**:
 
 - [`deno`](https://deno.land) To run project (code, ci, ...).
+- [`mkcert`](https://github.com/FiloSottile/mkcert) To get https self signed
+  certificate for localhost.
 
 **Using VSCode**: